Hypertension/High Blood Pressure Health Center

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Doing physical exercise.
• Having extreme emotional stress.
• Having surgery, injury, or illness.
• Taking certain medicines, such as aspirin, nitroglycerin, tricyclic antidepressants, tetracycline, theophylline, or some blood pressure medicines.
• Using nicotine, alcohol (ethanol), or cocaine.
• Taking nonprescription cough, cold, or sinus medicines.
• Eating or drinking foods with caffeine.

What To Think About

• This test is not done very often. The 24-hour urine test is better for finding high levels of catecholamines than a blood test. For more information on a catecholamine urine test, see the topic Catecholamines in Urine.
• Another test, called the clonidine suppression test, may be done to find out whether high blood pressure is caused by an adrenal gland tumor. The clonidine suppression test measures your blood catecholamine levels before and after you take a small dose of the high blood pressure medicine clonidine (Catapres). If a tumor is present, clonidine will not cause your catecholamine levels to change. If your high blood pressure is caused by other factors, clonidine will cause your catecholamine levels to go down.